Question

How do KCN and HCldiffer in bonding?

Compare and contrast colorimetry and spectophotometry . How would spectorphotometry be used to detect the cyanide ion? Please give me a full and complete answer. Thanks

Answer 1

Ionic bonds are between K⁺ and CN^- ( the bond between a metal and a non metal atom is ionic bond). The C and N in CN^- are bonded by covalent sigma and pi bonds

The bonding in HCl is covalent bond ( The bond between two nonmetal atoms is covalent bond)

Colorimetry and spectrophotometry are especially used to measure colour absorption by solutions.

The main difference between colorimeter and spectrophotometer is that colorimeter is a device which measures absorbance of specific colours, whereas a spectrometer measures transmittance or reflectance as a function of wavelength.

Colrimetry uses fixed wavelengths which are in the visible range(human eye can detect) , but spectrophotometry can use wavelengths in UV and IR( in spectrophotometry instrument determine the measurements.It extends the range of possible measurements beyond those that can be determined by the eye alone).

The absorbance of light is measured by colorimeter whereas the spectrophotometer measures the amount of light passes through the sample.

Detection of cyanide ion

In the spectrophotometric measurement, the cyanide is converted to cyanogen chloride (CNCl) by reaction of cyanide with chloramine-T at a pH less than 8. After the completion of the reaction a color is formed on the addition of pyridine-barbituric acid reagent. The absorbance is read at 578 nm for the complex formed with pyridine-barbituric acid reagent and CNCl. Thus detect the presence of cyanide

Another method for detection of cyanide ion

Cyanide determination is based on the reaction with p-nitrobenzaldehyde into a reactive cyanohydrin and the subsequent reduction of the tetrazolium blue . The final product of the reaction is a purple coloured compound derived from diformazan with a maximum absorption at 520 nm . The colour fully develops within 25 minutes and the formed colour is stable for 60 to 80 minutes.